A quartz piezoelectric crystal converts electrical energy to mechanical energy
and vice versa.
It won't convert electrical energy into an electromagnetic wave by itself.
Magnetostrictive material such as Terfenol-D will convert mechanical vibrations
into a fluctuating magnetic field.
This can generate an electromagnetic wave directly using the homopolar effect.
A piezoelectric transducer can be used to mechanically drive magnetostrictive
material to produce an EM wave.
Efficiency is several orders of magnitude greater than a wire antenna enabling
practical portable VLF transmitters.
73 de VA3VVV
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On Sat, 4/20/19, DK1IS <[email protected]> wrote:
Subject: Re: LF: NEW quarz resonated VLF antenna
To: [email protected], [email protected]
Received: Saturday, April 20, 2019, 5:15 PM
Am 19.04.2019
um 17:28 schrieb Clemens
Paul:
Do you think it is possible
for a more
true comparison to compare the quartz resonated wire
antenna
against he same wire resonated conventionally by an
inductor
regarding field strength and 3dB BW?
Hi Clemens and group,
here is the promised extension of my tests, for
better
comparability merged with the first results (my post
on the
reflector from 20190418):
Having no VLF quartz yet, I made some preliminary
tests with a
randomly available HC-6-U quartz, QRG 2434 kHz,
wavelength 123 m.
TX: Sythesizer Schomandl MG100M, 300 Hz ... 100
MHz, smallest
step 0.1 Hz, Ri = 50 Ohms, P = 10 dBm, output tied
to first leg
of quartz, alternatively direct to the antenna
wire
RX: Perseus SDR with an active rod antenna on
my garage, fed
by a solar system, no external wire connections,
air-line
distance 100 m to my shackAntena wire: 2 m
or 4 m, laid out in the shack, tied to second
leg of quartz, alternatively direct to the TX
outputalternatively antenna
wire only
resonated by two roller plus one fixed inductors
in series,
fed directly from the TX output
Results with 2 m antenna wire:
with quartz resonator: fres = 2,433,908.8 Hz, RX
level at
resonance = - 63,1 dBm, - 3dB-bandwidth = 48.3 Hz
resulting in Q
= 50391without quartz resonator: RX level =
- 85,4 dBm resulting in a
gain of 22.3 dB with quartzcomparision: my
13 m T-Marconi with top load 4 x 33 m, tuned
to 2434 kHz and fed by the synthesizer with 10 dBm
results in a
RX level of - 32.1 dBm ;-)with inductive tuning at 2,434,000 Hz:
RX level = - 60.1 dBm resulting in a gain of 3dB
compared with
quartz. -3 dB-bandwidth = 249 kHz resulting in a
loaded Q =
9.8
Results with 4 m antenna wire:
with Quartz resonator: fres = 2,433,773.6 Hz, RX
level at
resonance = - 59 dBm. - 3 dB-bandwidth = 49.4 Hz
resulting in Q
= 49376without quartz resonator: RX level =
- 75.4 dBm resulting in a
gain of 16.4 dB with quartzwith indctive tuning at 2,234,000 Hz: RX
level = - 57.3 dBm resulting in a gain of 1.7 dB
compared with
quarz. - 3 dB-Bandwidth = 390 kHz resulting in a
loaded Q =
6.2
With all tests there was no additional resistive
matching at the
TX output. The tests at resonance showed the usual
unbalance
between lower and upper - 3 dB-points. With L-tuning
the upper is
further away from the resonance frequency than the
lower. With
quartz-tuning this effect is contrawise and of course
absolutely
much lesser accented. At a first glance L-tuning
offers advantages
due to its comparable huge bandwidth and the higher
fieldstength
at the RX site but this could shrink if you really go
down to VLF
frequencies, very short antennas and short distances.
According to
the author´s claims the quarz resonated system is
usable for short
range communication only and there the Q of L-tuned
antennas will
also grow to high values as well as the losses in the
tuning
circuit.
As soon as my ordered XTALs will arrive I´ll make
further tests
in the 4 kHz-range. If the results happen to differ
very much from
the preceding tests at 2.4 MHz I´ll report about
it.
73 es Happy Easter,
Tom, DK1IS
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